1. Field of the Invention
This invention relates to a buffer circuit for use in, for example, impedance conversion, an input unit for current feedback type operational amplifiers and the like.
2. Related Background Art
Heretofore, the buffer circuit is composed of diode-connected transistors 15 and 16 which are opposite to each other in polarity, transistors 17 and 18 matching those transistors 15 and 16 respectively, and constant-current sources 19 and 20 for feeding constant current to the transistors 15 and 16 as shown in FIG. 1.
In the above conventional example, however, the transistors 15 and 17, and the transistors 16 and 18, for which matching is required respectively, are operated by a different C-E (Collector-Emitter) voltage. Therefore, an offset appears between input (IN) and output (OUT) due to the Early's effect of transistors, possibly causing a malfunction.